The present invention pertains to the art of microbial decontamination. It finds particular application in conjunction with sterilizing medical equipment with liquid sterilants and will be described with particular reference thereto. It will be appreciated, however, that the invention is also applicable to disinfecting systems as well as to microbial decontamination systems using fluid, e.g., gas or liquid, anti-microbial agents for sterilizing, disinfecting, or decontaminating a wide range of items, including dental instruments, endoscopes, laboratory equipment, manufacturing equipment, and other equipment and items on which it is desirable to eliminate microbial life forms.
Sterilization connotes the absence of all life forms, including bacterial endospores which are the living organisms most resistant to conventional sterilants. Disinfection, by distinction, only connotes the absence of pathogenic life forms. Microbial decontamination is generic to both sterilization and disinfection.
Medical equipment is often sterilized at high temperatures. Commonly, the equipment is sterilized in a steam autoclave under a combination of high temperature and pressure. Endoscopes, rubber and plastic devices or portions of devices, such as lenses, and the like may be destroyed or have their useful lives severely curtailed by this heat and pressure.
More sensitive medical equipment is often sterilized with ethylene oxide, which is thermally less severe than steam. The items must be exposed to the ethylene oxide for a relatively long duration, on the order of three and a half hours. Thereafter, eight to twelve hours are normally required for de-gassing or desorbing the ethylene oxide from plastic and other materials which are capable of absorbing the ethylene oxide. The pressurization and depressurization cycles of ethylene oxide sterilization may damage lens systems and other delicate instruments. Moreover, the ethylene oxide is relatively expensive. It is sufficiently toxic and volatile that extensive precautions are commonly taken to assure operator safety.
Liquid systems are used for sterilizing and disinfecting a wide variety of instruments, including instruments which are too heat sensitive or delicate for heat sterilization. A suitable liquid sterilization system is illustrated in prior U.S. Pat. No. 5,091,343 of the assignee herein. In the system of the earlier patent, items to be sterilized are inserted or placed in the tray of a cassette. A cover is placed on the cassette and the cassette is placed in a liquid sterilization unit. Within the unit, the cassette is filled with liquid sterilant, rinsed with a sterile rinse, and the rinse water drained. As the rinse water drained, sterile air is introduced to refill the cassette. Thereafter, the cassette is removed with its lid still in place such that the sterilized instruments are maintained in a sterile environment until the cassette is opened. Although this prior system has been successful, one of the drawbacks has been in assuring a flow of liquid sterilants through interior passages of medical instruments. The low pressure circulation of the liquid sterilant in the cassette did not assure sterilization of internal passages.
In accordance with the present invention, a new and improved anti-microbial apparatus and cassette therefor are provided which overcomes the above-referenced problems and others.